1. Field of the Invention
The present invention relates to an exposure method and an exposure apparatus to be used when a mask pattern is transferred onto a substrate in the lithography step for producing devices including, for example, semiconductor elements, liquid crystal display elements, plasma display elements, and thin film magnetic heads. The present invention also relates to techniques in relation to the above.
2. Description of the Related Art
High exposure accuracy is required for the exposure apparatus of the full field exposure type (stepper type) or the scanning exposure type (for example, the step-and-scan system) to be used in order to produce semiconductor elements or the like. Therefore, the exposure apparatus adopts arrangements which make it possible to perform highly accurate positioning or highly accurate scanning for the reticle stage system for positioning the reticle as a mask and for the wafer stage system for two-dimensionally moving the wafer as a substrate respectively. The reticle stage system and the wafer stage system have been hitherto assembled successively and directly on a predetermined frame mechanism.
In order to further enhance the resolution, the recent exposure apparatus uses the exposure light beam of the ArF excimer laser (wavelength: 193 nm) having the wavelength shorter than that of the KrF excimer laser (wavelength: 248 nm). Further, it has been investigated to use, for example, the F2 laser beam (wavelength: 157 nm) having the shorter wavelength. However, the vacuum ultraviolet light (VUV light) as described above, which has the wavelength of not more than about 200 nm, has a high absorbance for ordinary air (especially oxygen). Therefore, when the vacuum ultraviolet light is used as the exposure light beam, it is necessary to adopt the following procedure. That is, respective stage systems are tightly enclosed in stage chambers (sub-chambers) respectively, and the gas such as nitrogen gas or helium gas, which has a high transmissivity with respect to the vacuum ultraviolet light, is supplied into the stage chambers. Alternatively, the optical path of the exposure light beam at the inside of the stage chambers is substantially in vacuum. Such a procedure is also adopted in the same manner as described above for the space between adjacent lenses which are arranged at the inside of the projection optical system. Accordingly, it is necessary to adopt the following procedure for the exposure apparatus which uses the vacuum ultraviolet light as the exposure light beam. That is, the projection optical system is installed to the frame mechanism, and the respective stages are successively assembled. After that, the corresponding stage chambers are installed so as to surround the respective stage systems while maintaining the air-tightness.
The exposure apparatus, which uses, for example, the vacuum ultraviolet light as the exposure light beam as described above, is assembled by installing the stage chambers for maintaining the air-tightness after successively assembling the projection optical system and the respective stage systems with respect to the frame mechanism. However, the method, in which the respective stage systems, the stage chambers, and other components are successively assembled with respect to the single flame mechanism as described above, requires a considerable period of time to assemble and adjust the apparatus. Further, a long period of time is required, for example, to adjust the relative positions between the respective stage systems and the projection optical system. Therefore, an inconvenience arises such that the production cost of the exposure apparatus is increased. Further, the method, in which the respective stage systems, the respective stage chambers, and other components are successively assembled as described above, involves the following inconvenience as well. That is, the adjusting process is also complicated when the maintenance is performed for the exposure apparatus. As a result, the time and the cost required for the maintenance are increased.
Further, when it is intended to easily assemble and adjust the exposure apparatus with the arrangement in which the gas having a high transmissivity with respect to the exposure light beam is supplied, for example, to the inside of the respective stage chambers, the following fear occurs. That is, the amount of leak of the gas having the high transmissivity is increased, the concentration of the gas is decreased on the optical path of the exposure light beam, and the intensity of the exposure light beam is lowered on the substrate to be exposed therewith. When the gas having the high transmissivity is an expensive gas such as helium gas, it is necessary to utilize the gas as effectively as possible in order to suppress the running cost.
It is also required for the exposure apparatus of the scanning exposure type that the exposure apparatus is easily assembled and adjusted, and especially the throughput of the exposure step is increased. In relation to the above, when the scanning exposure is performed by synchronously moving the reticle as the mask and the wafer as the substrate, the operations of acceleration, movement at a constant velocity (scanning velocity), and deceleration are performed for each of the reticle stage and the wafer stage. It has been hitherto considered to be sufficient that the scanning velocity is merely increased, in order to increase the throughput of the scanning exposure operation. However, if the scanning velocity is increased, it is necessary to prolong the acceleration time and the deceleration time. Therefore, the high throughput is not necessarily obtained merely by increasing the scanning velocity.
Taking the foregoing problems into consideration, a first object of the present invention is to provide an exposure method and an exposure apparatus in which stage systems and other components are easily assembled and adjusted.
A second object of the present invention is to provide an exposure method and an exposure apparatus in which stage systems and other components are easily assembled and adjusted, and a gas, which transmits an exposure light beam, is supplied to at least a part of an optical path of the exposure light beam, wherein the gas is effectively utilized to make it possible to maintain a high concentration of the gas on the optical path.
A third object of the present invention is to provide an exposure method and an exposure apparatus in which stage systems and other components are easily assembled and adjusted, and the positional relationship between the respective components is successfully measured easily and correctly.
Another object of the present invention is to provide an exposure method and an exposure apparatus which make it possible to increase the throughput when the scanning exposure is performed.
Still another object of the present invention is to provide a method for efficiently producing the exposure apparatus as described above, and a method for producing devices to make it possible to produce a variety of devices at the low cost or the high throughput by using the exposure apparatus.
Still another object of the present invention is to provide a stage module which is capable of being detachably attached to the exposure apparatus.
According to a first aspect of the present invention, there is provided an exposure apparatus for exposing a second object (W1) with an exposure light beam passing through a first object (R1), the exposure apparatus comprising:
a frame (32 to 37);
a first stage chamber (23) which accommodates a first stage system which carries the first object while holding the first object, the first stage chamber being detachably installed to the frame; and
a second stage chamber (38) which accommodates a second stage system (WST) which carries the second object while holding the second object, the second stage chamber being detachably installed to the frame.
In the exposure apparatus according to the present invention as described above, the first and second stage chambers are constructed as modules. The exposure apparatus can be assembled and adjusted easily and quickly by assembling the first and second stage chambers, for example, in parallel, and then installing them to the frame mechanism. Further, the first and second stage chambers can be easily detached from the frame mechanism. Therefore, it is also easy to perform the maintenance for the exposure apparatus.
In this arrangement, it is also preferable that a projection system (PL), which projects an image of a pattern on the first object onto the second object, is installed to the frame, and the second stage system to be used is a double-stage system including a first substrate stage (40A) which drives a first substrate (W1) as the second object, and a second substrate stage (40B) which drives a second substrate (W2) as the second object.
The frame includes, for example, a first base member (32, 39) on which the second stage chamber is placed, a second base member (35) which is arranged on the first base member with a vibration-preventive pedestal (34) intervening therebetween and on which the first stage chamber is placed, and a third base member (37) which is arranged on the first base member with a vibration-preventive pedestal (36) intervening therebetween and to which the projection system is installed. The vibration, which is generated in each of the stage systems, does not make any harmful influence to other portions, by allowing the vibration-preventive pedestals to intervene as described above.
It is desirable that the apparatus further comprises a gas supply apparatus (4 to 6, 7A, 7B) which supplies a gas for transmitting the exposure light beam therethrough, to the inside of the first stage chamber, the second stage chamber, and the projection system; a first covering member (18C) which seals (substantially isolates from the atmospheric air) space between the first stage chamber and the projection system; and a second covering member (18D) which seals (substantially isolates from the atmospheric air) space between the projection system and the second stage chamber. For example, the first and second stage chambers are installed to the frame mechanism, and then the two covering members are installed. Thus, it is easy to decrease the amount of leak of the gas transmitting the exposure light beam therethrough, from the optical path of the exposure light beam ranging from the inside of the first stage chamber to the inside of the second stage chamber, and it is possible to maintain a high intensity of the exposure light beam.
It is also preferable that the exposure apparatus of the present invention is provided with a transport chamber (70) in which a transport system (WRDA) for transporting the second object into the second stage chamber is accommodated; and a gas supply apparatus (4 to 6, 7A, 7B) which supplies a gas for transmitting the exposure light beam therethrough, to the inside of the first stage chamber, the second stage chamber, and the transport chamber respectively to make control so that the concentration of the gas for transmitting the exposure light beam therethrough in the second stage chamber is higher than that in the transport chamber. Accordingly, it is possible to decrease the amount of use of the gas on condition that the transmissivity of the exposure light beam is increased.
The exposure apparatus may further comprise gas supply tubes which connect the first stage chamber, the second stage chamber, and the transport chamber to the gas supply apparatus respectively, solenoid-operated valves which are provided for the respective gas supply tubes, and a gas control system which controls operation of the solenoid-operated valves. The exposure apparatus may further comprise a sensor which measures a concentration of a light-absorbing substance in the first stage chamber, the second stage chamber, and the transport chamber, wherein the gas supply apparatus may supply the gas to the first stage chamber, the second stage chamber, and the transport chamber on the basis of the concentration of the light-absorbing substance measured by the sensor. Each of the second stage chamber and the transport chamber may be provided with an opening for receiving the second object, an opening for feeding the second object, and a shutter for closing the opening for feeding the second object. The shutter may be divided into two in the vertical direction, and the opening degree of the opening may be regulated depending on the size of the second object.
According to the second aspect of the present invention, there is provided an exposure apparatus for exposing a second object (W1) with an exposure light beam passing through a first object (R1), the exposure apparatus comprising:
a first stage chamber (23) which accommodates a first stage (RST) which moves the first object;
a first measuring system (25Y) which measures a position of the first stage (RST) in the first stage chamber (23);
a second stage chamber (38) which accommodates a second stage (WST) which moves the second object (W1);
a second measuring system (50AY) which measures a position of the second stage (WST) in the second stage chamber (38); and
a main measuring system (54Y, 57Y) which measures positions of the first stage chamber (23) and the second stage chamber (32).
According to the exposure apparatus as described above, the positions of the respective stages in the first and second stage chambers are measured by the first and second measuring systems respectively. The positions of the respective stage chambers are measured by the main measuring system. Therefore, it is possible to measure the positional relationship between the respective stage systems easily and correctly.
In this arrangement, the exposure apparatus may further comprise a projection system (PL) which projects an image of a pattern on the first object onto the second object; wherein the main measuring system may include a third measuring system (54Y) which measures a positional relationship between the first stage chamber and the projection system, and a fourth measuring system (57Y) which measures a positional relationship between the second stage chamber and the projection system. Accordingly, it is possible to highly accurately measure the positions of the respective stages and the positional relationship thereof on the basis of the projection system.
The exposure apparatus according to the present invention may further comprise a main control system (200), wherein the main control system may determine the position of the first stage from measurement results obtained by the first measuring system and the third measuring system, and it may determine the position of the second stage from measurement results obtained by the second measuring system and the fourth measuring system. The main control system may drive the first stage and the second stage while controlling the positions or velocities of the first and second stages on the basis of the determined positions of the first stage and the second stage.
In this arrangement, the first measuring system may be attached to a side surface of the first stage chamber, and the second measuring system may be attached to a side surface of the second stage chamber. The first to fourth measuring systems may be first to fourth interferometers respectively, a reflecting mirror for the third interferometer may be attached to an outer surface of the first stage chamber, and a reflecting mirror for the fourth interferometer may be attached to an outer surface of the second stage chamber. Especially, the reflecting mirror for the third interferometer may be attached to the first interferometer embedded in a side wall of the first stage chamber, and the reflecting mirror for the fourth interferometer embedded in a side wall of the second stage chamber may be attached to the second interferometer.
According to a third aspect of the present invention, there is provided an exposure apparatus for exposing a second object with an exposure light beam passing through a first object while synchronously moving the first object (R1) and the second object (W2), the exposure apparatus comprising:
a stage system which moves one of the first object and the second object; and
a main control system which controls the stage system so that the one of the first object and the second object is accelerated at a predetermined rate of acceleration until a predetermined scanning velocity is obtained, and the one of the first object and the second object is moved at the predetermined scanning velocity, wherein:
the scanning velocity is determined so that exposure time is substantially shortest depending on the rate of acceleration.
In the exposure apparatus according to this aspect, assuming that LY represents a width of a comparted area (29) in a scanning direction to be exposed by one time of scanning exposure for the first object or the second object as the driving object, D represents a width (slit width) of an exposure area (28) in the scanning direction to be exposed with the exposure light beam for the driving object, Wxcex1 represents the rate of acceleration, and VW represents the scanning velocity; the scanning velocity VW is determined, for example, so that a value of xcex94T, which is defined by the following expression, is substantially minimum.
xcex94T=2xc2x7VW/Wxcex1+(LY+D)/VWxe2x80x83xe2x80x83(1)
The first term of the exposure time xcex94T is the sum of the acceleration time and the deceleration time, and the second term is the time (exposure time in narrow definition) in which the exposure is performed at the scanning velocity VW in the exposure area for the comparted area. That is, when the scanning velocity VW is increased, then the exposure time in the narrow definition is shortened, but the acceleration and deceleration time is prolonged. Therefore, the scanning velocity is optimized so that the highest throughput is obtained, by determining the scanning velocity VW so that the sum xcex94T of the both is shortest.
According to a fourth aspect of the present invention, there is provided a method for producing an exposure apparatus for exposing a second object (W1) with an exposure light beam passing through a first object (R1), the method comprising:
a first step of assembling a frame (32 to 37);
a second step of assembling a first stage system which moves the first object, accommodating the first stage system in a first stage chamber (23), and detachably installing the first stage chamber to the frame; and
a third step of assembling a second stage system which moves the second object, accommodating the second stage system in a second stage chamber (38), and detachably installing the second stage chamber to the frame. According to the method for producing the exposure apparatus as described above, it is possible to efficiently produce the exposure apparatus according to the first aspect of the present invention. Especially, the first stage system and the second stage system can be assembled separately from the frame, and then they can be installed to the frame together with the stage chambers. Therefore, it is easy to perform the operation for assembling the precise stage. It is also easy to perform the maintenance operation after the assembling.
It is desirable that the method further comprises a fourth step of installing, to the frame, a projection system (PL) for projecting an image of a pattern on the first object onto the second object, wherein a cutout (38a), through which the projection system is capable of passing, is provided beforehand at an upper portion of the second stage chamber, and the second stage chamber and the projection system are relatively moved in the fourth step. Accordingly, the second stage chamber and the projection system can be installed to the frame mechanism easily and highly accurately.
According to a fifth aspect of the present invention, there is provided an exposure method for exposing a second object with an exposure light beam passing through a first object, the exposure method comprising:
moving, in a first stage chamber, a first stage which holds the first object, while irradiating the first object with the exposure light beam; and
moving, in a second stage chamber, a second stage which holds the second object, in synchronization with the first stage, wherein:
the first stage chamber and the second stage chamber are modules which include a first stage system having the first stage and a second stage system having the second stage respectively. The exposure method further comprises supplying, to the first stage chamber and the second stage chamber, a gas which does not substantially absorb the exposure light beam.
According to a sixth aspect of the present invention, there is provided an exposure method for exposing a second object with an exposure light beam passing through a first object with an exposure apparatus provided with a first stage which moves the first object and a second stage which moves the second object in synchronization with the first object, the exposure method comprising:
measuring a position of the first stage at the inside of a first stage chamber which accommodates the first stage;
measuring a position of the second stage at the inside of a second stage chamber which accommodates the second stage;
measuring positions of the first stage chamber and the second stage chamber in the exposure apparatus respectively; and
exposing the second object with the exposure light beam passing through the first object, while controlling the positions or velocities of the first stage and the second stage, on the basis of the measured positions of the first stage and the second stage and the measured positions of the first stage chamber and the second stage chamber. In this exposure method, when the first stage and the second stage are synchronously moved to perform the exposure, the positions of the stages are determined on the basis of the positions in the stage chambers and the positions of the stage chambers. The positions or the velocities of the stages are controlled in accordance with the determined positions. Therefore, the positions of the stages are adjusted relatively easily when the exposure apparatus is assembled. The exposure apparatus to be used may further comprise a projection system which projects a pattern on the first object onto the second object. In this case, the positions of the first stage chamber and the second stage chamber in the exposure apparatus are a position of the first stage chamber with respect to the projection system and a position of the second stage chamber with respect to the projection system. Further, the position of the first stage with respect to the projection system may be determined from the measured position of the first stage at the inside of the first stage chamber and the position of the first stage chamber with respect to the projection system, and the position of the second stage with respect to the projection system may be determined from the measured position of the second stage at the inside of the second stage chamber and the position of the second stage chamber with respect to the projection system.
According to a seventh aspect of the present invention, there is provided an exposure method for exposing a second object with an exposure light beam passing through a first object, while synchronously moving the first object and the second object, the exposure method comprising:
accelerating the first object or the second object at a predetermined rate of acceleration until a predetermined scanning velocity is obtained; and
irradiating the first object with the exposure light beam, while moving the first object or the second object at the scanning velocity, wherein:
the scanning velocity is determined so that exposure time is substantially shortest depending on the rate of acceleration. In this exposure method, the scanning velocity is optimized so that the highest throughput is obtained, by determining the scanning velocity so that the exposure time is minimum as expressed by the expression (1).
According to an eighth aspect of the present invention, there is provided a stage module comprising:
a stage apparatus which moves an object while holding the object;
a stage chamber which accommodates the stage apparatus; and
a measuring system which is attached to a wall surface of the stage chamber and which measures a position of a stage in the stage chamber. The stage module according to the present invention accommodates the stage apparatus, and the module can be detachably attached to an exposure apparatus. Therefore, when the stage apparatus is assembled to the exposure apparatus, it is sufficient to attach the stage module to a frame of the exposure apparatus. It is easy to perform the operation for producing the exposure apparatus. The stage module may further comprise a loader chamber which accommodates a loader for charging the object into the stage chamber, the loader chamber being connected to the stage chamber. It is noted that the stage module resides in a concept which includes the stage chamber and the stage apparatus accommodated therein as a kit. It is also preferable to use a module structure in which a stage apparatus is already supported (arranged) on a bottom surface of a box-shaped stage chamber as described later on. It is also preferable that no specified connecting relationship is formed between a stage chamber and a stage apparatus. In the case of the latter, when the stage module is assembled, for example, to a frame of an exposure apparatus, it is possible to successively assemble the stage apparatus and the stage chamber to the frame.
According to another aspect of the present invention, there is provided a method for producing a device, comprising the step of transferring a mask pattern (R1, R2) onto a workpiece (W1, W2) by using any one of the exposure apparatuses according to the present invention. According to the present invention, it is possible to produce a variety of devices at low cost or at high throughput.